Wikipedia 10K Redux by Reagle from Starling archive. Bugs abound!!!

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The theory that the mental can be reduced (see ReducTion) to the physical is usually called physicalism.  It is also called materialism or identity materialism.  The term "physicalism" is less misleading because it does not have any misleading connotations; if we called the view "materialism," you might think that we were talking about something that had to do with the desire for wealth, possessions, and so forth, but obviously we’re not talking about that.  We’re talking about a theory about the mind.  "Physicalism" is better also because it implies that the mental can be reduced to whatever is physical, meaning, whatever is described ultimately by physics; and as we all know, physics describes a lot more than just matter, it also describes energy.  So the view is that we can reduce mental events to events that are made up entirely of matter and energy.  And remember what we mean by "reduce" here: "If I reduce X to Y, then whenever I talk about X, I can be understood to be talking about Y instead."  So here’s the claim: Whenever we talk about mental events, we can be properly understood to be talking about events that are made up entirely of matter and energy.

I suppose that this sounds very strange.  I know it sounded very strange the first time I heard it.  So let me give you an example, and I’ll try to make this as plausible as I can.  In fact there is a hackneyed example that is used when philosophers talk about this stuff.  For some reason philosophers these days always use pain as an example of a mental event; why not pleasure, I say?    There is supposed to be a certain kind of nerve fiber that leads from your limbs to your brain, called C-fibers, and whenever you’re in pain, the story goes, your C-fibers are firing; and whenever your C-fibers are firing, then you’re in pain.  I suppose we might test this claim empirically, with experiments, right?  Suppose I sit you down in my lab, and I insert some probe into your spine, right next to your C-fibers; then I find some clever way to cause you pain.  You say, "Ouch!" and tell me that you are in pain.  I say, "Good!" and sure enough I see that your C-fibers are firing.

My apologies if I’m getting the facts all wrong.  But the point is in some such way, we are supposed to be able to study which neural states, and brain states, are associated with which mental states.  Now surely that would be very interesting if we were to find that, in order to be in pain, we would have to have firing C-fibers -- wouldn’t it?  For that matter, a neuroscientist might notice that when you engage in deep thought, the frontal lobe of your brain is extremely active.  When we engage in reasoning and complex conceptualization, the neurons in a certain part of the brain are firing; that seems to indicate that there is some sort of close association between hard thought and frontal lobe activity.

So the suggestion now is that the event of feeling pain is just the same as C-fibers firing.  That is why Halverson calls the theory "identity materialism"; types of mental events, like pain, are identical to types of physical events, like C-fiber firing.  So, pain is reducible to C-fiber firing.  This particular theory is also called "the type-type identity theory," since mental event types are matched up with physical event types.  And mind you, again, not just matched up or associated with -- but actually the very same as.  The pain I experience when I bash my thumb with a hammer is really nothing more than those C-fibers going off.

Now, some of you might hear this and think that I am denying that pain, or anything mental, really exists.  In other words, since I’m saying now that mental events are really only physical events, you think that I’m saying there aren’t any mental events.  But that is not my claim.  Mental events do exist; they are simply identical to physical events of a certain kind.

It so happens that there is a theory about the mind, called eliminativism, which says that the mind, mental events, and all the rest of that simply do not exist.  The best-known proponent of this theory is an American, Paul Churchland.  He says that this talk of mental events, thinking and such, is all just a fiction, just folks tales, which is going to be replaced with more scientific talk, when the science of the brain and the nervous system is sufficiently developed.  When that time comes, the eliminativists say, we won’t use this out-dated talk of feelings, thoughts, pains, etc.  We’ll talk about C-fibers firing, and frontal lobes being activated, and so forth.  All that talk of love, hate, decisions, beliefs, and so forth, will look antiquated and silly in the same way that talk of ghosts, demons, and witches now looks antiquated and silly.  I’m not even going to tell you why some philosophers buy into this theory -- it’s pretty unpopular, as you might have guessed -- I’m just telling you that it exists, so I can contrast physicalism with it.  Physicalism does hold that mental events exist.

Nonetheless, you still might think that physicalism is a very strange theory, that is totally contrary to common sense.  So you might object, as follows.  This will be the only objection to physicalism I’ll state, but it’s rather complex.  Just remember now all those differences that we listed between mental and physical events.  Mental events are not publicly observable; they are not spatially located; they do not involve physical properties such as mass and velocity; and there is seems to be an irreducibly subjective aspect to them.  How on earth could anyone say that mental events are just the same as physical events?  There are all these obvious differences, so you can’t reduce the mental to the physical!  So physicalism has to be wrong.

Here is how the physicalist would reply.  Let’s go over each of those alleged differences between mind and matter.  The first one is: mental events are not publicly observable.  The physicalist would say: well, OK, so mental events cannot be seen by other people; but neither can the sorts of physical events we’re talking about.  A C-fiber firing is not only buried inside your nervous system; it is also not detectable except with special instruments.  So we could very well say that C-fiber firing is not publicly observable.

If you’re a dualist, you’re probably not going to be happy with this reply.  You’ll probably say that the physicalist is missing the point.  The point is really that mental events aren’t observable by other people at all.  Other people can’t jump into my mind and as it were mentally look over my shoulder while I’m feeling pain and having deep thoughts.  Maybe Mr. Spock can do that but you and I can’t.  So, you, or a dualist, might say, what follows from that?  What follows is that feeling pain can’t be the same as C-fibers firing; other people can probe my nervous system and observe my C-fibers firing but they definitely aren’t observing my pain, no matter how carefully they observe my C-fibers or any other part of my nervous system.  It doesn’t  matter; my mental states can’t be observed by other people at all!  That’s how I think the dualist would reply.

How do you suppose the physicalist counter that?  Let me play the role of the physicalist.  So I would reply by saying that, really, if "publicly observable" just means "observable by other people," then your mental states are publicly observable.  Mental events can be observed by other people.  So what exactly would I be doing, then, if I did observe your pain?  Would I have to feel your pain myself?  In other words, in order for me to observe your pain, would I have to have the same aches and hurts that you have?  Surely not.  Why would you think that?  In order for me to observe your pain, it seems to me I simply have to observe the fact that you are in pain.  And if, as a physicalist, I hold that pain is the same as C-fibers firing, then all I have to do is observe your C-fibers firing, and voila -- I am observing the fact that you are in pain.  The dualist isn’t going to be at all happy with this reply; but let’s leave that debate and move on to those other supposed differences between mind and body.

The second difference is that mental events are not spatially located.  So here’s how the dualist will object to physicalism on that point: mental events are not spatially located, but physical events are spatially located.  So mental events are obviously different from physical events.

Here’s how I, the physicalist, can reply to that point.  I can concede that, for example, when I make a decision, I do not see or otherwise perceive my decision as being located anywhere.  I am just immediately aware of my decision, once I’ve made it.  But does that mean that the event of my decision in fact isn’t located anywhere?  I mean, simply because I’m not aware of its location, does it follow from that, that my decision doesn’t have a location at all?  I don’t see how that follows.  Why can’t we just say: a decision is a certain type of event in the brain.  When this event occurs, I’m aware of making a decision.  But I am not aware of where the decision itself is taking place, namely in my brain.  That doesn’t mean that the decision isn’t taking place in my brain.  Why think that?

OK, let’s look at the third alleged difference between the mental and the physical.  The third difference is: mental events do not involve physical properties such as mass and velocity.  The physicalist would say that neural events have electro-chemical properties; but the dualist would reply that the very idea of a mental event being a physical event in the brain and nervous system is absurd, precisely because that would mean that mental events have electro-chemical properties, and other physical properties as well.

I’ll bet some of you can predict how our physicalist will reply.  As the physicalist, I will say: "Why is that absurd?  Let me try to figure out why you think it’s absurd that mental events might have physical properties.  Maybe you think that since you’re not aware of any electro-chemical properties of your mental events, it somehow follows that your mental events don’t have any such properties.  But once again, that inference just doesn’t follow.  It assumes that, if all your pains, decisions, and thoughts had some electro-chemical properties, then you’d be aware of those properties.  But why think that?  Do you have to be aware of all of the properties that your mental events have?  Do you have to be aware of everything that is true of the processes of your mind?  Of course not.  There is a lot of unconscious stuff going on in your mind, a lot of stuff you’re not aware of.  So then, why not think that your decisions, your pains, and other mental events have electro-chemical properties?  The only thing that would make that suggestion absurd is if you thought you had to be aware of everything going on in your mind.  But you don’t have to be aware of everything going in your mind.

Finally, let’s look at the fourth supposed difference between the mental and the physical.  It is probably the hardest to deal with: there seems to be an irreducibly subjective aspect to mental events.  In other words, there is a first-person, felt, immediate, personal, subjective aspect to mental events.  Physical events do not have this subjective aspect; physical events are not qualia.  When dualism claims this, it is basically throwing down the gauntlet to physicalism.  "Look," the dualist says, "there just is this subjective aspect to my pain; it makes sense to ask, ‘What does your pain feel like?’  But it doesn’t make sense to ask, ‘What does your C-fiber firing feel like?’  C-fiber firing does not have this subjective aspect.  So you can’t reduce pain to C-fiber firing."

How could a physicalist reply to this?  Well, I think it’s not as difficult a problem as some might like to make it out to be.  If I’m a physicalist, then my claim is that C-fiber firing, or maybe some other brain event, just is awareness of pain.  And so it follows, of course, that C-fiber firing, or the brain event, does have a subjective aspect; and that it does make sense to ask, "What does your C-fiber firing feel like?"

But once again, the dualist is likely to say, "OK, say we open you up and look at your C-fibers firing away.  Are we going to see this subjective aspect, the pain qualia that we talked about?"  Well, the answer to that is clearly no.  But is that a problem?  After all, we experience pain only if it’s our C-fibers that are firing.  If you open my spine up and use scientific instruments to look at my wildly firing C-fibers, then of course you won’t be experiencing pain.  In order for you to experience pain, your C-fibers would have to be firing.  So here’s the point then: the dualist wants to object that a physical event cannot have a subjective aspect; the physicalist protests and says there’s no good reason not to think that physical events can have subjective aspects.  Why couldn’t they?  We can detect a physical event in someone else without ourselves being in a subjective state.  But so what?  Why should I expect to be in pain when I see someone else’s C-fibers fire?  It’s only the firing of my own C-fibers that constitutes my own pain.  So, President Clinton to the contrary notwithstanding, he cannot feel my pain!

So on all four counts, the physicalist has a way to explain how these supposed differences between the mental and the physical aren’t really differences at all.  This undermines crucial support for dualism and greatly increases the plausibility of physicalism.  It is not so absurd, or at least not so obviously absurd, to say that types of mental events are the same as, and reducible to, some types of physical events.  We just have to put these issues in the right light.  And physicalism has one very clear advantage over dualistic interactionism, namely, that there is no mystery about how the interaction between mental and physical events takes place.  Right?  Simply because mental events are, at bottom, themselves types of physical events.